Hillary Clinton has said she hopes there will be a women president in her lifetime, fuelling speculation she plans to run in 2016.

The former secretary of state can barely say a word without it being examined for signs it means she will give the presidency another shot - and the audience at the private Toronto meeting greeted her comments as the strongest hint yet.

"Let me say this, hypothetically speaking, I really do hope that we have a woman president in my lifetime," Clinton said at a women's conference on Thursday night.

"And whether it's next time or the next time after that, it really depends on women stepping up and subjecting themselves to the political process, which is very difficult."

Clinton said one of her "great predecessors" as first lady, Eleanor Roosevelt, said for women to be in politics "they need to grow skin as thick as an rhinoceros".

"I think there is still truth to that, so you have to step up, you have to dare to compete, you have to get into the process and then the country, our country, has to take that leap of faith," she said.

Clinton said the election of Barack Obama in 2008, who beat her to the Democratic nomination in a bruising battle to succeed George W. Bush, was an "historic" moment that was "incredibly important for obvious reasons".

And she said the election of a female president would also send "exactly the right historic signal". Clinton added: "I will certainly vote for the right woman for president."

When asked recently whether 2016 would see another Clinton run for the presidency, former president Bill Clinton replied with a joke: "Chelsea's still too young."